Designbold is an online application that allows you to create design elements without relying on a desktop application. The application is template-based, similar to Canva -- the best-known competitor in the field. The free version will store your images in the cloud and offers a wide range of design functions. To create a YouTube video thumbnail using Designbold, log in to your account. If you don't have a Designbold account, create a new one. For the purpose of creating a YouTube thumbnail, the free version of Designbold should cover most people's needs.